Insider Buys Of The Week: Cancer Genetics, Dish Network, Valvoline

• Insider buying can be an encouraging signal for potential investors.
• A notable CEO and another executive had established trading plans kick in this week.
• Another CEO and fellow insiders took advantage of an offering of common shares.

Conventional wisdom says that insiders and 10 percent owners really only buy shares of a company for one reason -- they believe the stock price will rise and they want to profit from it. So insider buying can be an encouraging signal for potential investors, particularly during periods of uncertainty.

Here's a look at a few notable insider purchases reported in the past week.

Dish Network

A DISH Network Corp DISH executive vice president purchased added another 25,000 shares of this pay-TV provider early last week. At an average of $28.01 a share, the transaction totaled more than $700,300. The executive made similar purchases earlier in the month and at the end of December, pursuant to a 10b5-1 trading plan.

Competitor Netflix, Inc. NFLX announced price hikes and posted mixed quarterly results last week. Dish shares closed Friday at $29.80, ending the week with an almost 7-percent pop. They've traded as low as $23.22 and as high as $48.21 in the past 52 weeks. The consensus price target was last seen at $48.18.

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Valvoline

Valvoline Inc VVV saw CEO Sam Mitchell add to his stake. At per-share prices that averaged $20.78, the 25,000 shares reportedly acquired altogether cost him around $519,500. That brought his stake to more than 167,000 shares, and it also was pursuant to a 10b5-1 trading plan. Note that another executive sold more than 1,400 shares last week.

The company recently announced it will offer open recall checks to customers at participating service center locations. The stock ended last week at $21.90 per share, which was above Mitchell's listed purchase price. Valvoline shares have traded as high as $25.14 in the past year, but the consensus price target was at $21.91 on last look.

Cancer Genetics

CEO John Roberts and two directors at Cancer Genetics Inc CGIX took advantage of a common offering of stock. The total of 1.2 million shares purchased, at a share price of $0.23, came to $270,000 altogether. The CEO's stake was said to be 112,200 shares, though one of those directors has a stake of more than 3.7 million shares.

The company recently shared a business update with shareholders that included a "strategic transaction" to be announced later in the quarter. Shares were trading at $0.28 a share on last look, so the purchases seem well-timed. Shares have changed hands as high as $2.20 apiece in the past year.